Knowledge of the structure of viruses and how they interact with the cells they infect is essential to broadening our understanding of the critical events in the infection process. Structural studies inform the development of therapeutic interventions to counter the diseases caused by viruses, for example by blocking viral entry or the spread of virus particles between cells. Virus replication and virus particle formation are complex, multistage processes involving the products of many viral genes. CVR researchers are using cryo-electron microscopy and three-dimensional image reconstruction techniques to investigate the structures of several families of viruses at different stages of their replicative cycles to elucidate the relationship between form and function. These studies are combined with molecular genetic analyses to produce comprehensive descriptions of the processes occurring at particular stages during their replicative cycles. Current projects include the analysis of genome content and organisation in ortho and paramyxoviruses; receptor binding patterns and recognition sites in adenoviruses and caliciviruses; cellular replication sites in hepaciviruses; and the DNA packaging machinery in herpesviruses.